Question

The average kinetic energy of $O_2$ at a particular temperatures is $0.768$ eV. The average kinetic energy of $N_2$ molecules in eV at the same temperature is?

• A. $0.0015$
• B. $0.0030$
• C. $0.048$
• D. $0.768$

Answer 1

The correct option is D $0.768$

Ideal gas law, says that

$PV=NKT$.

This means that:

Average Kinetic Energy, $K_{avg}=\frac{3}{2}kT$

This is a very important fact, as it tells the fundamentals about the temperature. The absolute temperature of the ideal gas is directly proportional to the average kinetic energy. So, changes in pressure and/or volume will result in changes in temperature too. Also, we can see that the average kinetic energy of the ideal gas

molecule will depend on temperature only and not on the gas nature/mass. Therefore, if the temperature is the same, then the kinetic energy of $O_2$ and $N_2$ both will be equal.

Hence average K.E. for $N_2$ will also be 0.768 eV.

Option D is correct.